1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method for processing a substrate with a process liquid. Examples of substrates to be processed include semiconductor wafers, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FEDs (field emission displays), substrates for optical discs, substrates for magnet-optical discs, glass substrates for photomasks, substrates for ceramics, substrates for solar cells, etc.
2. Description of Related Art
JP-A-2009-147038 discloses a substrate processing apparatus which comprises a spin chuck that holds a substrate in a horizontal position and rotate the substrate, a chemical liquid dispense nozzle for dispensing a chemical liquid onto the substrate held by the spin chuck, and a rinsing liquid dispense nozzle for dispensing a rinsing liquid onto the substrate which already have been processed by chemical liquid. The chemical liquid dispense nozzle is connected via a chemical liquid valve with a chemical liquid supply unit which is so configured as to dynamically vary flow rates of the chemical liquid.
With this configuration, the following steps are performed: a first step for supplying the chemical liquid from the chemical liquid dispense nozzle toward a surface of the substrate at a first flow rate while the substrate being rotated by the spin chuck at a first rotational speed; a second step for decreasing the substrate rotational speed into a second rotational speed that is slower than the first rotational speed while maintaining the flow rate of the chemical liquid; and a third step for decreasing a flow rate of chemical dispense liquid into a second flow rate while maintaining the substrate rotational speed at the second rotational speed. In the first step, the whole surface of the substrate is being covered with the chemical. In the second step, a heap of the chemical liquid is being formed. In the third step, newly provided chemical liquid is being supplied onto the heap.
The chemical supply unit described in JP-A-147038 has a configuration so as to be able to dynamically change flow rate of chemical liquid. But in order to do so, the chemical supply unit must be provided with a flow control valve; which is expensive and responsible for a considerable increase of overall costs.